Messages in this thread |  | | From | Con Kolivas <> | Subject | Re: patch-O1int-0306281420 for 2.5.73 interactivity | Date | Sun, 29 Jun 2003 14:57:40 +1000 |
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On Sun, 29 Jun 2003 11:32, Con Kolivas wrote: > On Sun, 29 Jun 2003 08:45, Roberto Orenstein wrote: > > On Sat, 2003-06-28 at 17:26, pat erley wrote: > > > I made a small error when I sent Con a piece of magic I wrote up to > > > help the sleep period. > > > > > > what it says right now: > > > > > > /kernel/sched.c around line 325 > > > > > > > > > sleep_period = (sleep_period * > > > 17 * sleep_period / ((17 * sleep_period / (5 * tau) + 2) * 5 * tau)); > > > ----------------------------------------------------------^ > > > > > > it should be: > > > > > > sleep_period = (sleep_period * > > > 17 * sleep_period / ((17 * sleep_period / (5 * tau + 2)) * 5 * tau)); > > > --------------------------------------------------------------^ > > > > > > stupid parenthesis. > > > > > > a little background. what this essentially is is a taylor > > > approximation of the function ln(66x+1) normalized. ln(66x+1) happens > > > to do a great job oas a weighting function on the range of 0 to 1, and > > > because the input only happens to range from 0 to 1, only 2 terms were > > > needed to do a 'good enough' job. > > > > > > Pat > > > > I did your correction and I got a kernel panic(attempting to kill init) > > on boot. It didn't flushed to disk, so it isn't attached, but it panics > > at effective_prio+0xcc/0xe0. > > With objdump I could see it traps a division by 0: > > cc: f7 fb idiv %ebx > > > > I remember cleary %ebx being 0 on the panic report. > > And I tracked down and the code is on this else in effective_prio: > > ----------- sched.c 341----------------- > > else { > > sleep_period = (sleep_period * > > 17 * sleep_period / ((17 * sleep_period / (5 * tau + 2)) * 5 * tau)); > > if (!sleep_period) > > return p->static_prio; > > } > > -------------------------------------- > > > > I don't have the time now to track this further today, but what happens > > if sleep_period is too small and tau is too big? > > Could this (17 * sleep_period / (5 * tau + 2) give 0 and so a division > > by 0? > > This will give a divide by zero. > > I will put together a new patch soon with this correction and appropriate > logic.
Further inspection of this code shows to me that the current version will do the job adequately. The full function Pat put together is a little more complicated and unfortunately falls over with integer logic. This one is a reasonable enough approximation.
So to summarise, if you still wish to test/use this patch, continue using the patch as posted unmodified called:
patch-O1int-0306290223
Con
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